A top Australian neurosurgeon of Indian origin says cell phones use is a greater threat to human health than smoking, which kills 5.4 million people each year.

Dr Vini Khurana, a neurosurgeon at the Canberra Hospital, told UK's Independent newspaper that there is growing evidence that using handsets for 10 years or more can double the risk of brain cancer. This, however, does not mean that smoking is better for health than using cellphones.

Dr Khurana says the cellphone threat is greater because far more people use cellphones than smoke worldwide, some of them starting use at the age of 3 years. Over 3 billion people use cellphones, which is three times higher than the one billion people who use tobacco.

In India, 250 million people use cellphones, second only after US's 256 million users. The threat came from cell phone radiation having the potential to heat the side of the head or thermo-electrically interact with the brain, while Bluetooth devices and unshielded headsets could convert the user's head into potentially self-harming antenna, said Dr Khurana.

He said there have been increased reports of brain tumours associated with heavy and prolonged mobile phone use, particularly on the same side as the person's "preferred" ear for making calls. Since cell phones were often a necessity, he says, people should use them as little as possible and called on the phone industry to make them safer.

The World Health Organisation says that cellphones are safe but admits there are "gaps in knowledge" that need further research about health impact in the longterm. Three large international reviews have investigated and found no conclusive link between use of cell phones and brain cancer, tumours of the brain or leukaemia, and other cancers.